1. Field of the Invention
The present invention relates to a compounded resin and the use of such compounded resin compositions to form extruded tubes, such as those used to line metal tubes in downhole tubular applications during oil and gas production, as well as in line pipe, flow line, and transportation line applications during oil and gas production and supply operations.
2. Description of Related Art
Typical oilfield tubulars are produced from steel and corrosion resistant alloys or materials. During production, injection, and disposal well operations, the tubulars are exposed to hydrocarbon fluids and gases which contain brine water, hydrogen sulfide, and carbon dioxide. The combinations of fluids and gases transmitted by oilfield tubulars under extreme temperatures and pressures create a variety of caustic and corrosive conditions that attack and corrode tubular goods. One solution to prevent corrosion of oilfield steel tubulars is to coat the inside of the tubular with a plastic layer or other corrosion resistant coating.
An alternative to prevent corrosion of oilfield tubulars is to insert a corrosion resistant liner into the steel tubular. Such liners may be made of polyvinyl chloride (PVC), polyethylene (PE), glass fiber reinforced epoxy resin (GRE), or other reinforced polymer resins. Typically, these liners are up to 45 feet long and have an outside diameter sized to tightly fit within the inside diameter of the steel tubulars or to loosely fit creating an annulus, which is subsequently grouted. The PVC and PE liners are limited in their use because they cannot withstand elevated temperatures.
GRE liners, which can withstand elevated temperatures are formed from glass filaments coated with resin and wound into the liner. In a typical filament winding process to produce GRE liners, a plurality of glass filaments (for example, 1,000-2,000 in number) is aligned into a single roving. A plurality of rovings is passed through a bath containing a curable resin composition and exits the bath coated with resin. A pan containing the resin bath is located on a carriage that moves laterally along the axis of a horizontally positioned steel pipe acting as a production mandrel. The resin coated rovings are wound over the preheated production mandrel. The winding is accomplished by rotating the mandrel and moving a carriage which dispenses several resin coated rovings from end-to-end of the mandrel so that the rovings are laid down in a criss-cross pattern. The angle that the rovings make with a vertical line is controlled to attain hoop strength and axial strength. The rovings are laid side-by-side from end-to-end along the mandrel to cover the mandrel and produce a coating of GRE thereon. The placement of the rovings from one end to another and back again is referred to in this manufacturing process as one circuit. The resulting liner is made by performing a specific number of circuits. When the winding is complete, the GRE resin system is cured by heating the mandrel. After the resin is cured, the mandrel is allowed to cool and retract from the GRE liner. The GRE liner is removed from the mandrel, and the resin is post-cured (i.e., in a curing oven) so that the liner attains the desired physical properties and is ready for use as a liner in a steel oilfield tubular. Conventional GRE liners can withstand temperatures in typical downhole production or injection service to about 121° C.
Recently, oilfield drilling has reached depths of 20,000 feet or more below the surface of the earth. At such deep levels, the bottom hole temperature may be as high as 218-232° C. At these depths, the resin in conventional GRE liners is known to fail in combination with the corrosives in the downhole environment. Although thicker fiberglass reinforced resin liners can overcome some of the problems experienced in deep well production, it is desirable to maintain the walls of such liners as thin as possible to maximize the volume of fluids or gases which pass through the steel tubulars.
Accordingly, a need remains for an oilfield tubular liner that can withstand temperatures and corrosive exposure above 121° C.; in fact, some applications may require continuous temperatures as high as 260° C. or greater. Additionally, the tubular liner should be made of materials or compounds that are able to perform or be compatible in the use environment without degradation in mechanical and thermal performance. In other words, the tubular liner must be able to resist environmental stress failure, which can be a complicated interaction of mechanical, thermal, and chemical properties of the material.
There remains a need for a resin composition that can be extruded in sufficient lengths to form dimensionally strong liners for use in high temperature tubular applications. Such liners should be able to withstand exposure to extreme temperatures and protect metal tubulars against corrosion.